The accident happened when a tractor-trailer hauling hay bales collided with a school bus south of Blue Hill, Neb., around 4:45 p.m. local time on Wednesday, the Webster County Sheriff's Department told NBC News. The vehicles burst into flames after the collision, officials said, killing both drivers and two students and injuring five other children.

The injured, all of whom were between the ages of 6 and 10, were taken to area hospitals; one, a seven-year-old girl, was flown by medical helicopter to Children's Hospital in Omaha, Sara Bockstadter, Webster County attorney, said Thursday. The girl was listed in serious condition on Thursday morning, reported NBC station WOWT.com.

The victims of the crash were identified Thursday as Travis Witte, 21, of Blue Hill, the driver of the truck; Marla Wentworth, 59, of Red Cloud, the driver of the school bus; and students Dustin Tesdahl, 18, and Caroline Thallman, 10, both of Blue Hill.

The Blue Hill Community School District serves kids from kindergarten through 12th grade. The district has set up a crisis center at the school to help students and their families, Bockstadter said.

“Our first concern is for the families of those affected by Wednesday’s events," Bockstadter said. “Our hearts go out to everyone who has been touched by this tragedy."